1. Field of the Invention
This invention relates to endovascular devices for occluding and/or stabilizing and sealing off vasculature or body passageways, tissue defects, and aneurysms. More particularly, the present invention relates to a catheter deliverable embolic device composed of a flexibly interconnected linear sequence of miniature beads.
2. State of the Art
Devices which occlude blood flow and/or initiate blood clotting, and which can be introduced into the body via a catheter are valuable for stopping bleeding or the threat of bleeding, cutting off blood supply to a diseased organ, reducing blood flow to an organ, occluding an arterial venous malformation (avm), rebuilding a defective organ, occluding an aneurysm, etc. Devices typically utilized for these purposes include coils or particles which are deployed through a catheter to a target site where arresting blood flow is desired. In addition, various solutions, such as injectable glue, may be delivered through the catheter either for assisting and accelerating clotting or in treating the medical problem.
Typical devices used in the past include platinum coils which were inserted into the catheters and then pushed therethrough to the target site using a conventional catheter guide wire as a xe2x80x9cplunger.xe2x80x9d The use of detachable coils appears to be gaining widest acceptance for aneurysm therapy, perhaps because of the ease and precision of control of the delivery and disposition of the coil at the desired occlusion site. The most common coil devices typically comprise 0.010xe2x80x3 to 0.018xe2x80x3 diameter helical coils of platinum wire, a length of the coil being twisted into larger compound coils of 1-2 cm diameter for packing into an aneurysm. One approach for delivering such coils to an occlusion site involves forming or attaching the coil at the distal end of a delivery device such as a guidewire, and then threading the coil and wire through a catheter until the coil is disposed at the occlusion site, such as the neck or opening of the aneurysm. There the coils are extended from the distal end of the catheter and placed or packed into the aneurysm cavity so as to form a mass which causes thrombogenesis and fibrogenesis, safely sealing the aneurysm to prevent rupture. The coils are then detached from the distal end of the delivery device, and the catheter is removed from the patient. Sometimes the thrombogenic coils are also provided with fibers or filaments which enhance their thrombogenecity.
Types of particles used in the past for occluding blood flow include hydrophilic particles that swell to a larger size when blood is absorbed. This swelling, of course, aids in stopping the flow of blood, assuming the positions of the particles are maintained.
However, known thrombogenic devices present some drawbacks. For example, it can be difficult to make thrombogenic coils stay in place. Because the coils are frequently made of metals with spring characteristics, the coils may tend to resist packing, and unwind out of the aneurysm. Then, like other implanted devices, the coils can migrate within the body, potentially causing trauma to body tissues or dangerous unwanted thrombosis. Likewise, hydrophilic particles also tend to become dislodged from the target site and migrate within the body.
Embolic devices, including coils, are also currently used in conjunction with cardiac revascularization procedures. In these procedures, one or more holes are made in the heart muscle itself by means of a needle, laser, or other cutting means. These holes may or may not extend completely through the heart wall so as to communicate with an interior chamber of the heart. Creating these holes initiates angiogenesis, which begins the formation of collateral blood vessels and capillaries which restore blood flow around damaged or blocked arteries to regions suffering from ischemia or inadequate blood flow. It is hypothesized that the holes promote angiogenesis through the natural release of angiogenic growth factors. Delivery into these holes using growth factors such as vascular endothelial growth factors (VEGF) may speed this process.
It would thus be desirable to have an embolic device which may be more easily packed into an aneurysm, and is less susceptible to migration within the body. It would also be desirable to have an embolic device which is unlikely to cause damage to body tissues with which it comes in contact.
It would further be desirable to have a device which can be firmly anchored into a hole formed in body tissue, and also provide means for delivering drugs which promote revascularization in the region of the hole.
It would also be desirable to have a thrombogenic or drug delivery device which dissolves within the body so as to prevent objects which could come loose and migrate through the body, potentially causing trauma or unwanted thrombogenesis.
The present invention addresses some of the above stated needs by providing a device comprising a linear sequence of flexibly interconnected miniature beads. The device generally comprises a flexible elongate filament having a linear sequence of miniature beads fixedly or slidably disposed thereon. The device is configured to allow the beads to compress together for pushing through a catheter to a target location, where the string of beads is extended beyond the distal end of the catheter, and the flexible string of beads may fold back upon itself so as to occupy a volume of space at the target location and initiate thrombogenisis there. In various embodiments, the string of beads may be configured as a drug delivery device, wherein the beads are porous or hollow, and contain a medicament for controlled release into the interior of the body. In yet another embodiment, the invention comprises a linear sequence of flexibly interconnected miniature beads having an anchor element on one end of the string for preventing migration of the string of beads.
The invention thus provides a new and improved embolic, vaso-occlusive, and drug delivery device which may be easily deployed to a target site in the human body and which is effective in inducing clotting or otherwise arresting blood flow. It also provides an embolic device which is less susceptible to expanding out of an aneurysm after being packed therein. The embolic device of the present invention is also less susceptible to migration within the body, and is less likely to cause damage or trauma to body tissues with which it comes in contact. The device may also be more firmly anchored to the site at which it is desired, and is more capable of packing a body cavity to completely thrombose it. The device may also deliver medicament to the site at which it is deployed within the body, whether functioning as an embolic device or not.
Other advantages and features of the present invention will be apparent to those skilled in the art, based on the following description, taken in combination with the accompanying drawings.